The present invention relates generally to wireless networks and, more particularly, to adaptive frequency hopping in a time-slotted based wireless network.
Existing industrial wireless systems such as ISA100.11a or WirelessHART enable reliable wireless communications with time-slotted frequency hopping approach and mesh network technology. However, they could receive large impacts of interferences from other wireless systems such as WiFi or Bluetooth because they use the same 2.4-GHz frequency band. The impact from WiFi interference is the most significant because WiFi uses broadband signals. To mitigate the impacts of interference from such other radio systems, the adaptive frequency hopping (AFH) approach has been proposed to dynamically change transmitting frequency channels based on measured channel conditions.
When AFH is applied for such industrial wireless systems, however, the following problems arise. The first problem relates to the application for a large scale wireless network. As the communication range is relatively large and there are many nodes which communicate with each other in the system, available channels at each node are different. This leads to large network complexity and large memory size in each device because each transceiver must have every frequency hopping pattern. The second problem relates to reliable and rapid interference detection. Interferences should be detected statistically for reliable measurements. As such, large measurement time will be required in order to qualify channel conditions. This means that when the interference is dramatically increasing, the network performance will degrade.